WASHINGTON -LRB- CNN -RRB- -- There is `` no remaining hope '' of finding six men trapped for almost a month in a Utah coal mine alive , a federal official said Saturday .

Isaac Arellano holds a candle and sings during a fundraiser for miners Tuesday in Price , Utah .

`` Over the past 25 days , the Mine Safety and Health Administration has exhausted all known options in our attempt to reach the six miners , '' Richard Stickler , head of the agency , said in a statement .

`` The thoughts and prayers of the dedicated professionals at MSHA are with the families . ''

Sympathy for the failed efforts also came Saturday from the White House .

`` Last night , a difficult decision was made to end the search , '' President Bush said in a statement . `` Laura and I are deeply saddened by this tragedy and continue to pray for the families of these men . ''

Labor Secretary Elaine Chao called the ordeal `` heartbreaking . ''

`` The grueling around-the-clock rescue operation that claimed three lives and injured six others has also taken a tremendous toll on the many brave rescuers and the local community , and our thoughts and prayers are with them all , '' Chao said in a statement .

After drilling seven holes into mine tunnels from the mountaintop above , there has been no sign of the miners -- and microphones have picked up no sound from the men . See a timeline of rescue efforts ''

Tests showed underground oxygen levels were too low to sustain human life .

`` We basically told the families that at this point in time we 've run out of options , '' Stickler said at a news conference late Friday .

`` We 've consulted with the people that we have here , we 've consulted with the technical support in Pittsburgh and we 've consulted with private consultants in terms of where we can go , '' he said .

`` And basically , through all the information we 've gleaned over the past nearly four weeks in terms of the conditions we found , in terms of the air readings we found down there and ... everything else , we just do n't know where else we can put a hole to get any other information . '' See photos of the rescue mission ''

There were no public statements Saturday from Bob Murray , president and CEO of Murray Mining , co-owner of the Crandall Canyon Mine , who was the outspoken face of the rescue operation for the first three weeks , then largely disappeared from public view .

Federal officials became the spokesmen . No one from Murray Mining was present at Friday 's news conference .

`` They are done . It 's finished , '' the attorney for the families said , according to the Saturday edition of The Salt Lake Tribune .

`` It 's a hard and bitter pill for our families , and there were quite a few tears shed , '' the newspaper quotes Colin King as saying .

The men were trapped during a collapse on August 6 , and it is not known whether they survived the cave-in .

Efforts to reach them were suspended 10 days later when two rescuers and a federal mining official were killed , and six people were injured in a second collapse as they tried to tunnel horizontally toward the area where the men had been working .

Murray said last week that the search effort would stop if no signs of life were found at the sixth hole .

Under pressure from the families , however , he agreed to try one more time . Families wanted officials to drill a hole large enough to send down a rescue capsule .

The effort to lower the robotic device down a seventh hole had been called `` a long shot '' by an official .

MSHA 's Stickler said that hole was drilled into the Crandall Canyon Mine on Thursday , but there were problems with a robotic camera that teams were trying to lower into it .

Work resumed Friday , this time at the fourth hole , but the camera could only descend about 7 feet , he said .

`` Basically , what it saw was really not that much . There was quite a bit of mud in there , water coming down the hole . It really could n't go any farther than seven feet , '' he said of the latest try . In addition , the roof was sagging .

`` The families asked many , many questions and we answered them all the best we could , basically coming to the conclusion that we had run out of options . ''

Murray said last Saturday he has already filed paperwork with federal regulators to permanently close and seal the Crandall Canyon mine .

`` I will never come back to that evil mountain , '' he said .

Friends and family have identified the six missing miners as Luis Hernandez , Manuel Sanchez , Kerry Allred , Carlos Payan , Brandon Phillips and Don Erickson . E-mail to a friend

@highlight

NEW : President Bush says he and first lady are deeply saddened by the tragedy

@highlight

Mine Safety and Health Administration chief : We 've run out of options .

@highlight

The six men have been trapped underground since August 6

@highlight

Seven bore holes drilled into the mountain have found no signs of life